OK, so the problem was there before the new plugs & wires, well maybe begin with suspecting the coilpack if you don't have any trouble codes. Remember that "Murphy's Law" is still in effect, so don't take the new plugs & wires off your suspect list just yet!!

Then maybe progress to looking for vacuum leaks & the intake manafold gaskets belong on your suspect list for vacuum leaks & fuel delivery, EGR system, or compression problems.

If you can come by a scantool, like an Actron CP9145, ect, that has a hook up cable for your OBD-1 system, that can read & display live sensor PID's to the computer & look at fuel trim numbers, MAF sensor & TPS sensor PID's to the computer, O2 sensor switching & any pending or set codes, those too may help shorten your trouble shoot. For instance, if the TPS doesn't signal the computer that the throttle is opening, the fuel mixture will go dead lean & can cause the engine to stumble.
Same for the MAF sensor or O2 sensors if they are lazy to react, so a scantool that'll read sensor output PID's to the computer can be a Big help in a trouble shoot.

You've been busy on this one & have covered a lot of the usual suspects, keep looking, you'll likely find the culprit.